Xjyuk

'sudo apt-get update' get a warning

Who are these characters/superheroes in the posters from Chris's room in Family Guy?

Is refreshing multiple times a test case for web applications?

Was this a rapid SCHEDULED disassembly? How was it done?

Write an interpreter for *

How do we avoid CI-driven development...?

Is it incorrect to write "I rate this book a 3 out of 4 stars?"

Double blind peer review when paper cites author's GitHub repo for code

What does Apple mean by "This may decrease battery life"?

sed delete all the words before a match

Acceptable to cut steak before searing?

Optimal way to extract "positive part" of a multivariate polynomial

Team goes to lunch frequently, I do intermittent fasting but still want to socialize

Dropdowns & Chevrons for Right to Left languages

How do I explain to a team that the project they will work on for six months will certainly be cancelled?

Non-OR journals which regularly publish OR research

Why level 0 espers are considered espers if they have no powers at all?

Why should we care about syntactic proofs if we can show semantically that statements are true?

Why are the inside diameters of some pipe larger than the stated size?

(11 of 11: Meta) What is Pyramid Cult's All-Time Favorite?

In a topological space if there exists a loop that cannot be contracted to a point does there exist a simple loop that cannot be contracted also?

Ex-contractor published company source code and secrets online

How can you evade tax by getting employment income just in equity, then using this equity as collateral to take out loan?

If a Contingency spell has been cast on a creature, does the Simulacrum spell transfer the contingent spell to its duplicate?

Invert bits of binary representation of number

Bit-twiddling for a custom image formatFinding patterns in a growing collectionMissing element from array (D&C) - code design/aesthetic improvementRotation of elements in an arrayByte array to floating point such as FPE2 in JavaBitfield class and Register depictionSieve of Eratosthenes for small limitsFind the longest length of sequence of 1-bits achievable by flipping a single bit from 0 to 1 in a numberChange Arithmetic Right Shift to Logical Right Shift

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;

3

$begingroup$

This is the code I came up with.

I added comments to make the solution more verbose.

int findComplement(int num) 
 // b is the answer which will be returned
 int b = 0;

 // One bit will be taken at a time from num, will be inverted and stored in n for adding to result
 int n = 0;

 // k will be used to shift bit to be inserted in correct position
 int k = 0;

 while(num)
 // Invert bit of current number
 n = !(num & 1);

 // Shift the given number one bit right to accesss next bit in next iteration
 num = num >>1 ;

 // Add the inverted bit after shifting
 b = b + (n<<k);

 // Increment the number by which to shift next bit
 k++;
 
 return b;

Is there any redundant statment in my code which can be removed? Or any other better logic to invert bits of a given integer

c++ mathematics bitwise

share|improve this question

asked 8 hours ago

KshitijV97KshitijV97

8066 bronze badges

$endgroup$

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  Are you re-inventing the binary not operator (~)?
  $endgroup$
  – Martin R
  8 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  I don't want to sound dumb, But honestly, I did not know that ~ operator existed which inverts all bits of a given integer.
  $endgroup$
  – KshitijV97
  8 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Many easy ways. ~num or -1 - num, or 0xFFFFFFFF - num, or 0xFFFFFFFF ^ num or (-1) ^ num. Doing it one bit at a time is most definitely the hard way.
  $endgroup$
  – AJNeufeld
  7 hours ago
  

  
  
  
  

add a comment | 

3

$begingroup$

This is the code I came up with.

I added comments to make the solution more verbose.

int findComplement(int num) 
 // b is the answer which will be returned
 int b = 0;

 // One bit will be taken at a time from num, will be inverted and stored in n for adding to result
 int n = 0;

 // k will be used to shift bit to be inserted in correct position
 int k = 0;

 while(num)
 // Invert bit of current number
 n = !(num & 1);

 // Shift the given number one bit right to accesss next bit in next iteration
 num = num >>1 ;

 // Add the inverted bit after shifting
 b = b + (n<<k);

 // Increment the number by which to shift next bit
 k++;
 
 return b;

Is there any redundant statment in my code which can be removed? Or any other better logic to invert bits of a given integer

c++ mathematics bitwise

share|improve this question

asked 8 hours ago

KshitijV97KshitijV97

8066 bronze badges

$endgroup$

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  Are you re-inventing the binary not operator (~)?
  $endgroup$
  – Martin R
  8 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  I don't want to sound dumb, But honestly, I did not know that ~ operator existed which inverts all bits of a given integer.
  $endgroup$
  – KshitijV97
  8 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Many easy ways. ~num or -1 - num, or 0xFFFFFFFF - num, or 0xFFFFFFFF ^ num or (-1) ^ num. Doing it one bit at a time is most definitely the hard way.
  $endgroup$
  – AJNeufeld
  7 hours ago
  

  
  
  
  

add a comment | 

$begingroup$

This is the code I came up with.

I added comments to make the solution more verbose.

int findComplement(int num) 
 // b is the answer which will be returned
 int b = 0;

 // One bit will be taken at a time from num, will be inverted and stored in n for adding to result
 int n = 0;

 // k will be used to shift bit to be inserted in correct position
 int k = 0;

 while(num)
 // Invert bit of current number
 n = !(num & 1);

 // Shift the given number one bit right to accesss next bit in next iteration
 num = num >>1 ;

 // Add the inverted bit after shifting
 b = b + (n<<k);

 // Increment the number by which to shift next bit
 k++;
 
 return b;

Is there any redundant statment in my code which can be removed? Or any other better logic to invert bits of a given integer

c++ mathematics bitwise

share|improve this question

asked 8 hours ago

KshitijV97KshitijV97

8066 bronze badges

$endgroup$

int findComplement(int num) 
 // b is the answer which will be returned
 int b = 0;

 // One bit will be taken at a time from num, will be inverted and stored in n for adding to result
 int n = 0;

 // k will be used to shift bit to be inserted in correct position
 int k = 0;

 while(num)
 // Invert bit of current number
 n = !(num & 1);

 // Shift the given number one bit right to accesss next bit in next iteration
 num = num >>1 ;

 // Add the inverted bit after shifting
 b = b + (n<<k);

 // Increment the number by which to shift next bit
 k++;
 
 return b;

share|improve this question

asked 8 hours ago

KshitijV97KshitijV97

8066 bronze badges

share|improve this question

asked 8 hours ago

KshitijV97KshitijV97

8066 bronze badges

asked 8 hours ago

KshitijV97KshitijV97

8066 bronze badges

asked 8 hours ago

KshitijV97KshitijV97

8066 bronze badges

1 Answer
1

active

oldest

votes

2

$begingroup$

int n = 0; This initialization is not used. It could simply be int n;, or could be int n = !(num & 1); inside the loop, to restrict the scope of n.

---

This loop:

int k = 0;
while (num) 
 ...
 k++;

could be written as:

for(int k = 0; num; k++) 
 ...

---

Since you are doing bit manipulation, instead of using addition, you should probably use a “binary or” operation to merge the bit into your accumulator:

 b = b | (n << k);

or simply:

 b |= n << k;

---

Bug

You are not inverting the most significant zero bits. Assuming an 8-bit word size, the binary compliment of 9 (0b00001001) should be 0b11110110, not 0b00000110. And the compliment of that should return to the original number (0b00001001), but instead yields 0b00000001.

---

And, as mentioned by @Martin R, you could simply return ~num;

share|improve this answer

answered 5 hours ago

AJNeufeldAJNeufeld

10.9k11 gold badge88 silver badges3333 bronze badges

$endgroup$

add a comment | 

Your Answer

StackExchange.ifUsing("editor", function ()
StackExchange.using("externalEditor", function ()
StackExchange.using("snippets", function ()
StackExchange.snippets.init();
);
);
, "code-snippets");

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "196"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);



);

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fcodereview.stackexchange.com%2fquestions%2f225897%2finvert-bits-of-binary-representation-of-number%23new-answer', 'question_page');

);

Post as a guest

Name

Email

Required, but never shown

2

$begingroup$

int n = 0; This initialization is not used. It could simply be int n;, or could be int n = !(num & 1); inside the loop, to restrict the scope of n.

---

This loop:

int k = 0;
while (num) 
 ...
 k++;

could be written as:

for(int k = 0; num; k++) 
 ...

---

Since you are doing bit manipulation, instead of using addition, you should probably use a “binary or” operation to merge the bit into your accumulator:

 b = b | (n << k);

or simply:

 b |= n << k;

---

Bug

You are not inverting the most significant zero bits. Assuming an 8-bit word size, the binary compliment of 9 (0b00001001) should be 0b11110110, not 0b00000110. And the compliment of that should return to the original number (0b00001001), but instead yields 0b00000001.

---

And, as mentioned by @Martin R, you could simply return ~num;

share|improve this answer

answered 5 hours ago

AJNeufeldAJNeufeld

10.9k11 gold badge88 silver badges3333 bronze badges

$endgroup$

add a comment | 

2

$begingroup$

int n = 0; This initialization is not used. It could simply be int n;, or could be int n = !(num & 1); inside the loop, to restrict the scope of n.

---

This loop:

int k = 0;
while (num) 
 ...
 k++;

could be written as:

for(int k = 0; num; k++) 
 ...

---

Since you are doing bit manipulation, instead of using addition, you should probably use a “binary or” operation to merge the bit into your accumulator:

 b = b | (n << k);

or simply:

 b |= n << k;

---

Bug

You are not inverting the most significant zero bits. Assuming an 8-bit word size, the binary compliment of 9 (0b00001001) should be 0b11110110, not 0b00000110. And the compliment of that should return to the original number (0b00001001), but instead yields 0b00000001.

---

And, as mentioned by @Martin R, you could simply return ~num;

share|improve this answer

answered 5 hours ago

AJNeufeldAJNeufeld

10.9k11 gold badge88 silver badges3333 bronze badges

$endgroup$

add a comment | 

$begingroup$

int n = 0; This initialization is not used. It could simply be int n;, or could be int n = !(num & 1); inside the loop, to restrict the scope of n.

---

This loop:

int k = 0;
while (num) 
 ...
 k++;

could be written as:

for(int k = 0; num; k++) 
 ...

---

Since you are doing bit manipulation, instead of using addition, you should probably use a “binary or” operation to merge the bit into your accumulator:

 b = b | (n << k);

or simply:

 b |= n << k;

---

Bug

You are not inverting the most significant zero bits. Assuming an 8-bit word size, the binary compliment of 9 (0b00001001) should be 0b11110110, not 0b00000110. And the compliment of that should return to the original number (0b00001001), but instead yields 0b00000001.

---

And, as mentioned by @Martin R, you could simply return ~num;

share|improve this answer

answered 5 hours ago

AJNeufeldAJNeufeld

10.9k11 gold badge88 silver badges3333 bronze badges

$endgroup$

int k = 0;
while (num) 
 ...
 k++;

for(int k = 0; num; k++) 
 ...

 b = b | (n << k);

 b |= n << k;

share|improve this answer

answered 5 hours ago

AJNeufeldAJNeufeld

10.9k11 gold badge88 silver badges3333 bronze badges

answered 5 hours ago

AJNeufeldAJNeufeld

10.9k11 gold badge88 silver badges3333 bronze badges

answered 5 hours ago

AJNeufeldAJNeufeld

10.9k11 gold badge88 silver badges3333 bronze badges